Inkjet-imageable lithographic printing members and methods of preparing and imaging them

ABSTRACT

Lithographic printing plates are imaged using an inkjet printer to imagewise apply a chemical or masking agent onto the plate surface. In some embodiments, the chemical causes an affinity change, thereby facilitating lithographic printing.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefits of U.S. ProvisionalApplication Ser. No. 60/617,695, filed on Oct. 12, 2004, the entiredisclosure of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates in general to lithography, and moreparticularly to lithographic printing members suitable for inkjetimaging.

BACKGROUND OF THE INVENTION

In offset lithography, a printable image is present on a printing memberas a pattern of ink-accepting (oleophilic) and ink-rejecting(oleophobic) surface areas. Once applied to these areas, ink can beefficiently transferred to a recording medium in the imagewise patternwith substantial fidelity. Dry printing systems utilize printing memberswhose ink-repellent portions are sufficiently phobic to ink as to permitits direct application. In a wet lithographic system, the non-imageareas are hydrophilic, and the necessary ink-repellency is provided byan initial application of a dampening fluid to the plate prior toinking. The dampening fluid prevents ink from adhering to the non-imageareas, but does not affect the oleophilic character of the image areas.Ink applied uniformly to the printing member is transferred to therecording medium only in the imagewise pattern. Typically, the printingmember first makes contact with a compliant intermediate surface calleda blanket cylinder which, in turn, applies the image to the paper orother recording medium. In typical sheet-fed press systems, therecording medium is pinned to an impression cylinder, which brings itinto contact with the blanket cylinder.

Lithographic plates can be fabricated in various ways, ranging fromtraditional manual techniques involving photoexposure and chemicaldevelopment to automated procedures involving computer control.Computer-to-plate systems can utilize pulses of electromagneticradiation, produced by one or more laser or non-laser sources, to createphysical or chemical changes at selected points of sensitized plateblanks (which, depending on the system, may be used immediately orfollowing conventional photodevelopment); ink-jet equipment used toselectively deposit ink-repellent or ink-accepting spots on plateblanks; or spark-discharge equipment, in which an electrode in contactwith or spaced close to a plate blank produces electrical sparks toalter the characteristics of certain areas on a printing surface,thereby creating “dots” which collectively form a desired image. Tocircumvent the cumbersome photographic development, plate-mounting, andplate-registration operations that typify traditional printingtechnologies, practitioners have developed electronic alternatives thatstore the imagewise pattern in digital form and impress the patterndirectly onto the plate.

Digital imaging of printing plates by inkjet printing is currentlywidely investigated; see, e.g., U.S. Pat. Nos. 6,526,886 and 6,691,618.The '618 patent, for example, discloses a method of imaging alithographic printing plate having an alkaline-soluble polymeric coatingwith a pH-elevating agent. The need to use alkaline solutions to developthese plates, however, poses environmental and safety problems. It wouldbe desirable to have inkjet-imagable lithographic printing plates thatcan be solely developed by water, or which do not require a developmentstep.

SUMMARY OF THE INVENTION

The present invention relates to lithographic printing members imagableusing a combination of inkjet and photopolymerization. An advantage tothis approach is the durability of photopolymer plates and the abilityto utilize conventional ultraviolet (UV) imaging sources.

Accordingly, in a first aspect, the invention provides a lithographicprinting member having a photosensitive top layer, an optionalcrosslinked intermediate layer, and a substrate thereunder, as well asmethods of imaging such a printing member. The top layer contains aphoto-polymerizable moiety and the first component of a two-componentphoto-polymerization initiating system. When reacted with an imagingfluid containing the second component of the two-componentphoto-polymerization initiating system and thereupon subjected toactinic radiation, the top layer undergoes photopolymerization andbecomes crosslinked. In some embodiments, the top layer is oleophilicand the substrate (or intermediate layer) is hydrophilic, whereas inother embodiments, the top layer is hydrophilic and the substrate (orintermediate layer) is oleophilic.

To provide a lithographic image, the imaging fluid is dispensed onto thetop layer of the printing member in an imagewise pattern. The imagedplate is then exposed to actinic radiation, allowing the imaging fluidto react with the photosensitive top layer and form a crosslinked imagedarea. The imaged printing member is then subjected to a solvent, such asan aqueous fluid, to remove non-image (i.e., uncrosslinked), portions ofthe top layer, leaving an imagewise lithographic pattern on the printingmember ready for inking.

Suitable photo-polymerizable moieties for forming the top layer include,but are not limited to, multifunctional acrylic monomers, oligomers,macromers, and combinations thereof. A suitable two-componentphoto-polymerization initiating system that can be used to prepare thetop layer and the imaging fluid is a hexaarylbiimidazole dimer with afree-radical-producing electron donor agent as a co-catalyst. Althoughnone of these compounds dissolves in water, it is believed that becausethe functional moieties only weakly adhere to the hydrophilicintermediate layer underneath, water may be applied to the top layer todisrupt the weak adhesion between the top and underlying layers, therebyallowing the removal of the non-image portions of the top layer. On theother hand, adhesion between the imaged areas, i.e., wherephotopolymerization and crosslinking have occurred, and the underlyinglayer is sufficiently strong that the imaged portions cannot be removedby water in the development step.

In a second aspect, the invention provides a printing member having asoluble top layer, an optional intermediate layer, and a substratethereunder, as well as methods of imaging such a printing member. Thetop layer, which contains a photoreactive reagent, becomes crosslinkedand water-insoluble when exposed to actinic radiation. An imaging fluidthat contains at least one of a photoreaction-inhibiting agent and amasking agent may be applied to the top layer, reducing or totallyinhibiting the reactivity of the photoreactive reagent and therebypreventing the imaged areas from undergoing crosslinking. In someembodiments, the top layer is oleophilic and the substrate (orintermediate layer) is hydrophilic, whereas in other embodiments, thetop layer is hydrophilic and the substrate (or intermediate layer) isoleophilic.

To provide a lithographic image, the imaging fluid is dispensed onto thetop layer of the printing member in an imagewise pattern. The imagedplate is then exposed to actinic radiation, which induces crosslinkingin the non-image areas, causing these areas to become water-insoluble.On the other hand, because the jetted fluid has masked the imagedportions from light and/or reacted within the imaged portions of the toplayer to reduce its photoreactivity, crosslinking does not occur in theimaged areas and a water-soluble image is formed in the top layer. Theimaged printing member is then subjected to a solvent, such as anaqueous fluid, to remove the imaged portions, leaving an imagewiselithographic pattern on the printing member ready for inking.

The photoreactive reagent found in the top layer can be aphoto-crosslinking agent or a photo-polymerization initiator. Suitablephoto-crosslinking agents include various bis-azides. Water-solublepolymers that can be crosslinked by bis-azides include, but are notlimited to, polyvinyl pyrrolidone, copolymers of vinyl pyrrolidone,acrylamide-diacetone acrylamide copolymer, polyacrylamide, copolymers ofacrylamide, gelatin, and mixtures thereof.

An alternative photo-crosslinking agent is a condensation product of anaromatic diazonium salt and a condensation agent. Suitable aromaticdiazonium salts include, but are not limited to, 4-diazodiphenylaminesulfate, 3-methoxy-4-diazodiphenylamine sulfate, 4-phenoxydiazobenzenezinc chloride double salt, and 2,5-dimethoxy-4-tolylmercaptodiazobenzenezinc chloride double salt. Water-soluble polymers that can becrosslinked by an aromatic diazonium salt-containing compound include,but are not limited to, polyvinyl alcohol, carboxymethylcellulose,hydroxymethylcellulose, hydroxyethylcellulose,hydropropylpropylcellulose, polyacrylic or methacrylic acid, polyvinylpyrrolidone, copolymers of vinyl pyrrolidone, polyacrylamide, copolymersof polyacrylamide, gelatin, and mixtures thereof.

Suitable photo-polymerization initiators include those that arewater-soluble. Examples include, but are not limited to, ceric ammoniumoxalate, manganic ammonium oxalate, and photoreducible dyes and theirco-catalysts. Another useful photoreactive reagent is a polyvinylalcohol comprising a stilbazolium moiety.

The imaging fluid may contain a photoreaction-inhibiting agent such asan antioxidant. Suitable antioxidants include, but are not limited to,hydroquinone, 4-methoxyphenol, 2,6-di-(t-butyl)-4-methylphenol,2,2′-methylenebis-(4-methyl-6-t-butylphenol), diesters ofthiodipropionic acid, and triarylphosphite. Alternatively, the imagingfluid may contain a masking agent that shields the imaged area fromexposure to actinic radiation. Suitable masking agents include variousdyes and pigments that absorb at wavelengths of photosensitivity of thephotosensitive top layer. Examples include, but are not limited to, AcidYellow 25 (C.I. 18835), Acid Yellow 29 (C.I 0.18900), Acridine Yellow G(C.I 0.46025), Basic Yellow 2 (C.I. 41000), Acid Black 2 (C.I. 50420),and aqueous dispersions of carbon black and yellow pigments. An imagingfluid that contains both a masking agent and a photoreaction-inhibitingagent may also be used according to the invention.

It should be stressed that, as used herein, the term “plate” or “member”refers to any type of printing member or surface capable of recording animage defined by regions exhibiting differential affinities for inkand/or fountain solution. Suitable configurations include thetraditional planar or curved lithographic plates that are mounted on theplate cylinder of a printing press, but can also include seamlesscylinders (e.g., the roll surface of a plate cylinder), an endless belt,or other arrangement.

Furthermore, the term “hydrophilic” is used in the printing sense toconnote a surface affinity for a fluid which prevents ink from adheringthereto. Such fluids include water for conventional ink systems, aqueousand non-aqueous dampening liquids, and the non-ink phase of single-fluidink systems. Thus a hydrophilic surface in accordance herewith exhibitspreferential affinity for any of these materials relative to oil-basedmaterials.

The term “fountain solution,” as used herein, pertains to a solutionused to clean or remove the water-soluble portions of the imagedprinting members of the methods of this invention and may be water,combinations of at least 90% water and 10% or less organic solvents andadditives such as alcohols, surfactants, and glycols, and buffered orsalt-containing neutral or nearly neutral water solutions. The term“fountain solution,” as used herein, does not include alkaline aqueoussolutions with a pH of greater than about 10, acidic aqueous solutionswith a pH of less than about 3.5, or organic solvents without at least90% by weight of water present.

Also, as used herein, the term “water-soluble” refers to a material thatcan form a greater than 1% solution in water or a mixture of awater-miscible solvent such as alcohol and water wherein the mixture ismore than 50% water.

As one of skill in the art will appreciate, features of one embodimentand aspect of the invention are applicable to other embodiments andaspects of the invention. The above-discussed and other features andadvantages of the present invention will be appreciated and understoodby those skilled in the art from the following detailed description anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing discussion will be understood more readily from thefollowing detailed description of the invention when taken inconjunction with the accompanying drawings.

FIG. 1 is an enlarged sectional view of an embodiment of anegative-working printing member according to the invention thatcontains substrate, a crosslinked hydrophilic intermediate layer, and aphotosensitive oleophilic top layer.

FIG. 2 is an enlarged sectional view of an embodiment of apositive-working printing member according to the invention thatcontains substrate, an oleophilic intermediate layer, an optionaladhesive layer, and a water-soluble hydrophilic top layer that isphotosensitive.

FIGS. 3A-3D are enlarged sectional views of the negative-workingprinting member of FIG. 1 illustrating an imaging mechanism according tothe invention.

FIGS. 4A-4D are enlarged sectional views of the positive-workingprinting member of FIG. 2 illustrating an imaging mechanism according tothe invention.

The drawings and elements thereof may not be drawn to scale.

DETAILED DESCRIPTION OF THE INVENTION 1. Imaging Apparatus

An imaging apparatus suitable for use in conjunction with the presentprinting members includes at least an inkjet printer. To facilitateaccurate imaging of the printing members according to the invention, thepaper-handling or substrate-handling subsystem of the inkjet printershould have a short, straight paper path. A printing plate is generallystiffer and heavier than the paper or media typically used incommercially available inkjet printers. If the construction of theprinter requires the printing plate to be bent before or after it ispresented to the imaging print head, then the movement of the printingplate through the printer may not be as accurate as the media for whichthe printer was designed. Printers such as the EPSON STYLUS COLOR 3000(available from Epson America, Inc., Long Beach, Calif.) have a suitablyshort, straight paper path. A platen is preferably placed at theentrance to the paper feed mechanism. The platen may have a registrationguide rail to support the plate as it is pulled into the printer by thefeed mechanism, facilitating the accurate transport of the plate underthe imaging print head.

The imaging apparatus may further include a developing processor forembodiments where off-press development of the imaged plate isenvisioned. U.S. Pat. No. 6,691,618, for example, describes a suitabledeveloping processor. The development process may involve conveying theimaged plate through a series of stations, which may include a hot airdryer, a pre-heat oven, a development station, a rinse station, and apost-bake oven. The plate is ready to be used on press after thisoff-press developing step.

In other embodiments, the imaged plate can be developed on-press. Inthese embodiments, after imaging of the printing member, no conventionaldevelopment of the latent image is required. Instead, the plate is firstheated in an oven to dry the image and, typically, to complete thereaction with the imaging fluid. Second, the plate is mounted on theplate cylinder of a conventional offset lithographic press. Third, thelatent image is developed by operating the press such that the platecylinder is rotated and the working fluids of the press, i.e., the pressink and fountain solution, are applied to the plate. The plate is thenready to be used to print images on paper or other media by the normaloperation of the press.

2. Inkjet Printing Process

Inkjet printing involves projecting tiny drops of ink fluid directlyonto the plate surface without physical contact between the inkjetprinter and the plate. The inkjet printer stores electrical datacorresponding to the image to be printed (specifically, the image orbackground area, depending on whether the plate is positive-working ornegative-working), and controls a mechanism for ejecting ink dropletsimagewise onto the plate. Printing is performed by moving the print headacross the plate or vice versa.

There are generally two mechanisms that commercially available inkjetprinters utilize to control how ink droplets are jetted. In continuousinkjet printing, the print head propels a continuous stream of inkthrough a nozzle. This stream is broken down into identical droplets,which are then selectively charged. Depending on the construction of theprinter, either the charged or the uncharged droplets are deflected andguided towards the receiving medium. The undeflected droplets arecollected and recycled. Continuous inkjet printers require complexhardware, but they offer high speed printing as an advantage.

In drop-on-demand inkjet printers, ink droplets are generated andejected through the orifices of the print head only as needed. Somedrop-on-demand systems use a thermal process to create the pressurerequired to eject ink droplets. These thermal jet (or bubble jet)printers use heat to generate vapor bubbles in a volatile component ofthe ink fluid. As these bubbles build up pressure and vaporize, inkdroplets are jetted out of the print head one at a time. Otherdrop-on-demand systems utilize a piezoelectric actuator to eject inkdroplets. In these printers, a computer signal imposes an electricalpotential across a piezoelectric material which causes it to deform. Inkdroplets are ejected as the piezoelectric material deforms and returnsto its normal dimensions. Although drop-on-demand inkjet printers haverelatively slow printing speed, they offer small drop size and highlycontrolled ink droplet placement.

The imaging step according to the invention can be performed by anysuitable inkjet printers and techniques described above. Commerciallyavailable drop-on-demand models are preferred, however, because of theirdurability and high resolution.

3. Lithographic Printing Members

A representative printing member according to the invention includes asubstrate, an optional intermediate layer, and a top layer. FIG. 1illustrates an embodiment of a printing member 100 according to theinvention that includes a substrate 102, a crosslinked intermediatelayer 104, and a photosensitive top layer 106 that is chemicallyreactive with an inkjet imaging fluid 108 (see FIGS. 3A-3D). In anegative-working version, the intermediate layer 104 is hydrophilic andthe photosensitive top layer 106 is oleophilic. In a positive-workingversion, the intermediate layer 104 is oleophilic and the photosensitivetop layer 106 is hydrophilic. FIG. 2 illustrates an embodiment of aprinting member 200 according to the invention that includes a substrate202, an intermediate layer 204, an optional adhesive layer, and asoluble top layer 206 that is photosensitive and chemically reactivewith an inkjet imaging fluid 208 (see FIGS. 4A-4D). In apositive-working version, the intermediate layer 204 is oleophilic andthe top layer 206 is hydrophilic. In a negative-working version, theintermediate layer 204 is hydrophilic and the top layer 206 isoleophilic.

Each of these layers and their functions will be described in detailbelow.

3.1 Substrate 102, 202

The substrate provides dimensionally stable mechanical support to theprinting member. The substrate should be strong, stable and, preferably,thin and flexible. One or more surfaces of the substrate can be eitherhydrophilic or oleophilic. Suitable substrate materials include, but arenot limited to, metals, polymers, and paper.

Metals suitable for use in substrates according to the inventioninclude, but are not limited to, aluminum, zinc, steel, chromium, andalloys thereof, which may have another metal (e.g., copper) plated overone surface. Metal substrates can have thicknesses ranging from about 50μm to about 500 μm or more, with thicknesses in the range of about 100μm to about 300 μm being preferred.

One or more surfaces of a metal substrate may be anodized. Anodizingincreases the hardness and abrasion resistance of the metal surface,which improves the mechanical strength of the substrate. The anodiclayer can also control dissipation of heat into the substrate, thusincreasing the imaging efficiency of the printing member. An anodizedaluminum substrate consists of an unmodified base layer and a porous,anodic aluminum oxide coating thereover. The anodized aluminum surfaceis hydrophilic; however, without further treatment, the oxide coatingwould lose wettability due to further chemical reaction. Anodizedsubstrates are, therefore, typically exposed to a silicate solution orother suitable reagent (e.g., a phosphate reagent) that stabilizes thehydrophilic character of the plate surface. In the case of silicatetreatment, the surface may assume the properties of a molecular sievewith a high affinity for molecules of a definite size andshape—including, most importantly, water molecules.

A preferred substrate is an anodized aluminum plate with a low degree ofgraining and an anodic layer having a thickness between about 0.5 μm andabout 3 μm (available, for example, from Precision Lithograining Corp.,South Hadley, Mass.). Graining can be achieved by methods known in theart such as by means of a wire brush, a slurry of particulates or bychemical or electrolytic means.

Polymers suitable for use in substrates according to the inventioninclude, but are not limited to, polyesters (e.g., polyethyleneterephthalate and polyethylene naphthalate), polycarbonates,polyurethane, acrylic polymers, polyamide polymers, phenolic polymers,polysulfones, polystyrene, and cellulose acetate. A preferred polymericsubstrate is a polyethylene terephthalate film such as MYLAR and MELINEX(available from E. I. duPont de Nemours Co., Wilmington, Del.).

Polymeric substrates can be coated with a transition layer to improvethe mechanical strength and durability of the substrate and/or to alterthe hydrophilicity or oleophilicity of the surface of the substrate. Ahydrophilic transition layer may include porous materials with oxygenfunctional groups at the surface. The addition of hydrophilic fillerssuch as, for example, silica particles, also enhances the hydrophilicityof the transition layer. Examples of suitable materials for hydrophilictransition layers according to the invention include proprietary hardcoat materials supplied by Bekaert Specialty Films, LLC (San Diego,Calif.). Other suitable formulations and application techniques fortransition layers are disclosed, for example, in U.S. Pat. No.5,339,737, the entire disclosure of which is hereby incorporated byreference.

Polymeric substrates can have thicknesses ranging from about 50 μm toabout 500 μm or more, depending on the specific printing memberapplication. For printing members in the form of rolls, thicknesses ofabout 200 μm are preferred. For printing members that include transitionlayers, polymer substrates having thicknesses of about 50 μm to about100 μm are preferred.

A wide variety of papers may be utilized as a substrate. Typically,papers are saturated with a polymeric treatment to improve dimensionalstability, water resistance, and strength during wet lithographicprinting.

In embodiments of the invention that do not include an intermediatelayer between the top layer and the substrate, the substrate and the toplayer (subsequent to reaction with the imaging fluid) generally haveopposite affinities for ink and/or a liquid to which ink will notadhere. In embodiments that do contain an intermediate layer, on theother hand, the substrate and the top layer (subsequent to reaction withthe imaging fluid) need not have opposite lithographic affinities.Instead, the intermediate layer is designed to have a lithographicaffinity opposite to that of the reacted top layer, as described below.However, it is generally preferable to provide a substrate and anintermediate layer of like affinities to promote adhesion and toaccommodate damage to the intermediate layer without loss ofperformance. Specifically, even though the intermediate layer istypically not soluble in aqueous solutions and is not removed during theimaging process, it can still be scratched or damaged during theprintmaking process. A substrate of like affinity will accept or rejectink in the same manner as the overlying intermediate layer in thoseareas where the intermediate layer is damaged, thus maintaining printquality and prolonging the press life of the printing member.

3.2 Intermediate Layer 104, 204

The intermediate layer is coated on the substrate. In embodiments wherea polymeric substrate is used, the intermediate layer can be thetransition layer described above. The intermediate layer can be eitherhydrophilic or oleophilic, provided that it has an affinity opposite tothat of the top layer after the top layer has reacted with the imagingfluid for at least one of ink and a liquid to which ink will not adhere.It should generally adhere well to the substrate and to the top layerand should withstand repeated application of fountain solution or inkduring printing without substantial degradation or solubilization. Theintermediate layer is optional in some embodiments.

Suitable materials for fabricating a hydrophilic intermediate layerinclude, but are not limited to, polyvinyl alcohol, polyacrylamide,polyvinyl pyrrolidone, and cellulosics. Polyvinyl alcohol is preferred.Homopolymers and copolymers with amine, carboxylic acid, sulfonic acid,and/or phosphonic acid moieties can also be used. Specific examplesinclude homopolymers and copolymers of vinyl alcohol withamino-functional groups, vinyl phosphonic acid, acrylamide, methylolacrylamide, methylol methacrylamide, acrylate acid, methacrylate acid,hydroxyethyl acrylate, hydroxyethyl methacrylate, and maleicanhydride/vinylmethylether copolymers. A polyceramic layer containingPVOH—ZrOH (see, e.g., U.S. Pat. Nos. 6,182,569, 6,182,570, and6,186,067) can also be used.

To increase toughness and wear resistance, the hydrophilic polymercoating is preferably crosslinked. Crosslinking agents such asformaldehyde, glyoxal, polyisocynate, melamine-type crosslinkers,ammonium zirconyl carbonate, titanate crosslinkers, hydrolyzedtetraalkylorthosilicate, and diepoxide crosslinkers can be added tocrosslink specific functional groups in the polymer. For example,diepoxide crosslinkers can effectively crosslink amino groups andcarboxylic acid groups. Polyvinyl alcohol can be crosslinked byhydrolyzed tetraethoxysilane according to procedures described in U.S.Pat. No. 3,971,660, by ammonium zirconium carbonate as described in U.S.Pat. No. 6,490,975, and by melamine with a catalyst such as an organicsulfonic acid.

The mechanism of the crosslinking reaction is not critical. For example,either radical-initiated crosslinking or oxidative crosslinking may beused.

In embodiments of the invention that include an oleophilic intermediatelayer, the materials used in the oleophilic coating should demonstrategood adhesion to the substrate below it and to the hydrophilic coatingthat is to be applied on top of it. Their oleophilic properties shouldbe such that, when placed on a press, the imaged areas accept inkimmediately. Run lengths in the order of thousands of impressions arepreferred. The oleophilic materials should therefore have suitabletoughness, wear resistance, and be non-reactive with the ink.

Many homopolymers and copolymers can be used as the oleophilicintermediate layer according to the invention. They includepolyurethanes, epoxy resins, polystyrene, copolymers of styrene,acrylics, copolymers of acetate and ethylene, polyacrylics, copolmyersof acrylics, polyvinyl acetate, phenol and cresol formaldehyde resins,cellulose ethers and esters, polyvinyl acetals, diazo resins, andsynthetic rubbers. They can be applied from a solvent solution, or canbe used in the form of an aqueous resin dispersion and be applied fromwater. Intermediate layers made from aqueous resin dispersions can beheat-treated to cause the dispersed resin particles to coalesce, whichincreases their toughness. In addition, commercially availablesubtractive coatings (e.g., subtractive plate NSSH manufactured byPrecision Lithograining, South Hadley, Mass.) with or without blanketlight exposure can be used as the oleophilic coating.

Other components that can be included in the intermediate layer arecolorants, plasticizers, surfactants, crosslinking agents and monomersincluding initiators. The latter two are added to increase toughness andcan be activated by either heat or light.

3.3 Top Layer 106, 206

The top layer receives the imaging fluid and is photosensitive asdescribed below. Materials utilized in this layer should exhibit goodadhesion to the layer below it, i.e., the intermediate layer or thesubstrate.

Materials forming the top layer can be applied to the intermediate layer(or, in embodiments where the intermediate layer is optional, thesubstrate) in any suitable manner using conventional coating equipmentand procedures. Upon drying, the top layer is generally at least 0.1 μmin thickness and can be as thick as 10 μm. Thus, in negative-workingembodiments of the present invention, the top layer should be thick andsubstantially continuous enough to provide the desired image upon fluidapplication, but not so thick that the non-image areas are difficult toremove after imaging. Similarly, in positive-working embodiments of thepresent invention, the top layer should not be so thick that the imagedareas are difficult to remove after imaging.

Apart from the components capable of reacting with the imaging fluid,the top layer may also contain various additives, e.g., nonionic and/oramphoteric surfactants, as appropriate to the application. Specificexamples of the nonionic surfactant include sorbitan tristearate,sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride,polyoxyethylene nonylphenyl ether, and the like. Specific examples ofamphoteric surfactants include alkyldi(aminoethyl)glycine, hydrochloricacid salt of alkylpolyaminoethylglycine,2-alkyl-N-carboxyethyl-N-hydroxyethylimidazolinum betaine,N-tetradecyl-N,N-betaine, and the like.

Dyes can be added in a small amount to adjust the plate color. Specificexamples of these dyes include Oil Yellow No. 101, Oil Yellow No. 103,Oil Pink No. 312, Oil Green BG, Oil Blue BOS, Oil Blue N. 603, Oil BlackBY, Oil Black BS, Oil Black T-505 (all marketed by Chemical Industries,Co., Des Moine, Iowa), Victoria Pure Blue, Crystal Violet (C.I. 42555),Methyl Violet (C.I. 42535), Ethyl Violet, Rhodamine B (C.I. 145170B),Malachite Green (C.I. 42000), Methylene Blue (C.I. 52015), and the like.

Further, if necessary, a plasticizer may be added to impart flexibilityto the top layer. Examples of suitable plasticizers include butylphthalyl, polyethylene glycol, tributyl citrate, diethyl phthalate,dibutylphthalate, dihexyl phthalate, dioctyl phthalate, tricresylphosphate, tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryloleate, an oligomer or a polymer of acrylic acid or methacrylic acid,and the like.

Specific embodiments of the top layer are discussed below.

3.4 Inkjet Imaging Fluid 108, 208

The inkjet imaging fluid contains at least one chemical compound in itscomposition which is either capable of reacting with, or inhibiting areaction in, the top layer. The chemical compound(s) may be present inthe imaging fluid in a concentration as high as 20% or even higher byweight, but preferably less than 5% by weight. It is also preferable,although not necessary, that the chemical compound(s) be in the form ofa homogeneous solution or a stable colloidal dispersion, so that it canpass through the nozzles of an inkjet print head.

The main liquid carrier can be water or an organic solvent orcombinations thereof. The choice of the liquid carrier depends on thespecific inkjet printer. Both aqueous-based and solvent-based fluids canbe used in the present invention depending on the inkjet technology thatis being used (i.e., piezo, thermal, bubble jet or continuous inkjet).

While water is the preferred medium for aqueous imaging fluids, theaqueous composition may comprise one or more miscible co-solvents, e.g.,a polyhydric alcohol. These co-solvents may be high-boiling humidifyingsolvents such as glycerin, propylene glycol, ethxylated glycerin,ethylene glycol, propylene glycol, diethylene glycol, triethyleneglycol, propylene glycol, dipropylene glycol, and trimethylol propane.The purpose of adding one or more high-boiling humidifying solvents isto prevent the imaging fluid from drying during idle periods which couldcause the inkjet nozzles to clog. Other high-boiling solvents can beadded to improve the solubility of the chemical compound tailored toreact with the top layer. Such solvents may include, but are not limitedto, methylpyrrolidone, propylene glycol monoethyl ether, propyleneglycol monobutyl ether, and propylene glycol ethyl ether acetate. Theamount of aqueous carrier medium in the aqueous composition may be inthe range from 30 to 99.995% by weight, preferably from 50 to 95% byweight.

Organic solvents that may be used as a carrier medium for the inkjetimaging fluid include, but are not limited to, alcohols, ketones oracetates.

As known in the art of the inkjet technology, the jet velocity,separation length of the droplets, drop size and stream stability isgreatly affected by the surface tension and the viscosity of the aqueouscomposition. Inkjet imaging fluids suitable for use with inkjet printingsystems may have a surface tension in the range from 20 to 60 dyne/cm,and preferably from 30 to 50 dyne/cm. Control of surface tensions inaqueous inkjet fluids may be accomplished by additions of small amountsof surfactants. The level of surfactants to be used can be determinedthrough simple empirical experiments. Several anionic and nonionicsurfactants are known in the inkjet art. Commercial surfactants includethe SURFYNOL series, e.g., SURFYNOL 104, SURFYNOL 45, SURFYNOL FS-80,SURFYNOL PSA-216 (available from Air Products, Allentown, Pa.); theDYNOL series, e.g., DYNOL 604 (available from Air Products, Allentown,Pa.); the TRITON series, e.g., TRITON X-100 (available from Rohm andHaas, Philadelphia, Pa.); the ZONYL series (available from E. I. duPontde Nemours Co., Wilmington, Del.); the FLUORAD series (available fromMinnesota Mining and Manufacturing Co., St. Paul, Minn.); the AEROSOLseries (available from American Cyanamid Co., Wayne, N.J.); and similarchemicals. The viscosity of the fluid is preferably not greater than 20mPA·s, e.g., from 1 to 10 mPA·s, preferably from 1 to 5 mPA·s at roomtemperature.

The inkjet imaging fluid may further comprise other ingredients. Abiocide may be added to prevent unwanted microbial growth which mayoccur in the fluid over time, and which would otherwise degrade theshelf life of the fluid. Suitable biocides include, but are not limitedto, PROXEL GXL (available from Zeneca Specialties, Manchester, UK),sodium OMADINE (available from Olin Mathieson Chemical Corp., New York,N.Y.), GIVGARD DXN (available from Givaudan Corp., New York, N.Y.),solution of 1,2-benzothiazoline-3-one, sodium hydroxide and dipropyleneglycol, 2-pyridinethiol-1-oxide, sodium salt, DOWICIL (available fromDow Chemical, Midland, Mich.),cis-1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride, andsimilar chemicals or mixtures of such chemicals. When used, the biocidewill typically be 0.1 to 3% by weight of the ink.

Additional additives that may be optionally present in the ink includethickeners, pH adjusters, buffers, conductivity-enhancing agents, dryingagents and defoamers.

Dyes may be added in order to enhance the image contrast after jettingthe image on the top layer. Many dyes and pigments are known to besuited for inkjet technology. Suitable dyes are further selected basedon their compatibility in the carrier medium (i.e., aqueous-based orsolvent-based) and on their compatibility with the reactive chemicalcompound, e.g., they should not lead to coagulation.

Specific embodiments of the imaging fluids and the compositions of thetop layers are discussed below in detail, along with the imagingtechniques associated therewith.

4. Imaging Techniques

4.1 Printing member 100 and imaging fluid 108

According to the embodiment illustrated in FIG. 1, the printing member100 includes a grained, anodized, and/or silicated aluminum substrate102, a crosslinked intermediate layer 104, and a photosensitive toplayer 106 that contains water-insoluble photo-polymerizable moieties.Upon reacting with the imaging fluid 108, imaged areas in the top layer106 become crosslinkable by exposure to actinic (e.g., UV) radiation.

Although the top layer 106 is water-insoluble, it is found that theprinting member 100 can be developed solely with water. Without beingbound by any particular theory or mechanism, it is believed that theadhesion between even an oleophilic top layer 106 and a hydrophilicintermediate layer 104 is sufficiently weak that when the plate 100 isexposed to water, the top layer 106 can be easily removed as watermolecules disrupt the weak adhesion between the top layer 106 and theintermediate layer 104. It is further believed that after imaging, theimaged areas in the top layer 106, i.e., where crosslinking hasoccurred, adhere significantly better to the intermediate layer 104,such that these imaged areas cannot be removed by water alone.

FIGS. 3A-3D illustrate the consequences of imaging an embodiment of theprinting member 100. As illustrated in FIG. 3A, an inkjet printer 110 isused to apply droplets of the imaging fluid 108 imagewise onto thephotosensitive and oleophilic top layer 106. The imaging fluid 108 wetsand penetrates the top layer 106, and creates an imaged area 112. Theimaged area 112 is then exposed to a source 120 of actinic radiation,such as a UV lamp, as shown in FIG. 3B. Upon radiation, the imagingfluid 108 reacts with the photosensitive top layer 106 and forms acrosslinked imaged area 124 that exhibits significantly strongeradhesion to the intermediate layer 104 than the non-image,non-crosslinked areas 144 a, 144 b. FIG. 3C shows that the imaged platecan be developed subsequently either on-press or off-press with water ora fountain solution 128, which disrupts the weak adhesion between thenon-image portions 134 a, 134 b of the top layer 406 and the underlyingcrosslinked layer 104. As shown in FIG. 3D, in a negative-workingversion, the fountain solution 128 wets layer 104 but is repelled by theimaged oleophilic area 124, which then accepts printing ink 138.

Suitable materials for forming the top layer 106 according to theinvention include a photo-polymerizable moiety, the first component of atwo-component photo-polymerization initiating system, and an optionalbinder. Examples of photo-polymerizable moieties include, but are notlimited to, multifunctional acrylic monomers, oligomers, macromers, andcombinations thereof. Hydrophilic moieties include polyvinyl alcohol,carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose,hydropropylpropylcellulose, polyethylene oxide, polyvinyl pyrrolidone,copolymers of vinyl pyrrolidone, polyacrylamide, copolymers ofpolyacrylamide, gelatin, and mixtures thereof, polystyrene sulfonicacid, polyacrylic or methacrylic acid, and mixtures thereof. Aromaticdiazonium salts may be added at low concentrations to improve adhesion.Inorganic pigments such as silica, alumina, clays, and titanium dioxidemay be added to improve the hydrophilic properties. Oleophilic moietiesinclude acrylate, methacrylate, and vinyl compounds of polyesters,polyurethanes, polyepoxides, bisphenol A resins, and phenoxy resinsamong others.

Suitable polymeric binders include, for example, polystyrene,(meth)acrylic polymers and copolymers (such as polybutylmethacrylate,polyethylmethacrylate, polymethylmethacrylate, polymethylacrylate,butylmethacrylate/methylmethacrylate copolymer), polyvinyl acetate,polyvinyl chloride, styrene/acrylonitrile copolymer, nitrocellulose,cellulose acetate butyrate, cellulose acetate propionate, vinylchloride/vinyl acetate copolymer, partially hydrolyzed polyvinylacetate, polyvinyl alcohol partially condensation-reacted withacetaldehyde, butadiene/acrylonitrile copolymer, and polyurethanebinder. Also useful are aqueous alkaline-soluble polymers, such as(meth)acrylic polymer with substantial number of carboxylic acidfunctional groups, polymers with substantial number of phenol groups,and polymers with (meth)acrylate groups and carboxylate salt groups asdescribed in U.S. Pat. No. 5,849,462.

Photo-polymerization initiators are compounds that generate radicalsunder the influence of added energy from actinic light. Somephoto-polymerization initiators require two different components.Examples of such two-component photo-polymerization initiating systemsare described in U.S. Pat. Nos. 3,615,567 and 3,479,185, the entiredisclosures of which are hereby incorporated by reference. These patentsdescribe a hexaarylbiimidazole dimer as a first component and afree-radical-producing electron donor agent as a second component thatact as co-synergists. Suitable free-radical-producing electron donoragents include, for example, methylene chloride, p-aminophenyl ketone,and N-phenylglycine. A preferred two-component photo-polymerizationinitiating system has 2,4,5-triphenylimidazolyl dimers consisting of twolophine radicals bound together by a single covalent bond andN-phenylglycine as a co-catalyst.

Suitable compositions for inkjet imaging fluid 108 include jettablefluids that contain the second component of the two-componentphoto-polymerization initiating system that readily reacts with thefirst component of the photo-polymerization initiating system in the toplayer 106 of the printing member 100 upon exposure to light to initiatecrosslinking and polymerization in the top layer 106.

4.2 Printing Member 200 and Imaging Fluid 208

In the embodiment illustrated in FIG. 4, the printing member 200includes a grained, anodized, and/or silicated aluminum substrate 202,an intermediate layer 204, and a soluble (e.g., water-soluble)photosensitive top layer 206. A thin adhesive layer 207 including adiazo resin may optionally be employed between the intermediate layer204 and the top layer 206. The top layer 206 generally becomescrosslinked and water-insoluble when exposed to actinic radiation.However, in areas of the top layer 206 where it has absorbed the imagingfluid 208, the photoreaction is inhibited and substantially does nottake place. In a positive-working version, top layer 206 is hydrophilicand intermediate layer 206 and/or substrate 202 is oleophilic. In anegative-working version, top layer 206 is oleophilic and intermediatelayer 206 and/or substrate 202 is hydrophilic.

FIGS. 4A-4D illustrate the consequences of imaging the positive-workingversion of the printing member 200. As illustrated in FIG. 12A, aninkjet printer 210 is used to apply droplets of imaging fluid 208imagewise onto the photosensitive top layer 206. The imaging fluid 208wets and penetrates the photosensitive top layer 206, and creates animaged area 212. The imaged plate 200 is then blanket-exposed to actinicradiation 220, e.g., ultraviolet light, as shown in FIG. 4B. Theultraviolet light induces crosslinking in the non-image areas 244 a, 244b, causing these areas to become water-insoluble. The jetted fluid 208inhibits crosslinking in the imaged area 212, so the imaged area 212remains water-soluble. FIG. 4C illustrates the imaged plate 200 that hasbeen developed by fountain solution or water. The developer dissolvesthe imaged area 212, and the underlying oleophilic layer 204 isrevealed. As shown in FIG. 4D, the fountain solution 228 adheres to thenon-image hydrophilic areas 244 a, 244 b, while the imaged oleophilicarea 224 accepts printing ink 238.

Accordingly, the top layer 206 comprises a material that is hydrophilicor oleophilic, soluble (preferably in water), and photosensitive.Suitable materials for preparing the crosslinkable top layer 206 includewater-soluble polymers with photo-crosslinking agents.

A suitable water-soluble photo-crosslinking agent such as bis-azide isparticular useful. An example of one such bis-azide is4,4′-diazidostilbene-2,2′-disodium sulfonate. Other water-solublebis-azides that can be used include, but are not limited to,4,4′-diazidobenzalacetone-2,2′-disulfonate disodium salt (described inU.S. Pat. Nos. 4,191,571, 1,3-bis(4′-azido-2′-sulfobenzylidene) butanonedisodium salt, 2,6-bis(4′-azido-2′-sulfobenzylidene) cyclohexanonedisodium salt,2,6-bis(4′-azido-2′sulfobenzylidene)-4-methylcyclohexanone disodiumsalt, 2,5-bis(4′-azido-2′-sulfobenzylidene) cyclopentanone disodiumsalt, 4,4′-diazidocinnamylideneacetone-2,2′-disodium sulfonate,2,6-bis(4′-azido-2′-sulfocinnamylidene) cyclohexanone disodium salt,2,6-bis(4′-azido-2′-sulfocinnamylidene)-4-methylcyclohexanone disodiumsalt, and 2,5-bis(4′-azido-2′-sulfocinnamylidene) cyclopentanonedisodium salt. In each of the disodium sulfonate compounds, the sodiumatoms may be substituted by other atoms or atomic groups such ashydrogen, ammonium, potassium, magnesium, calcium, barium, aluminum, andthe like.

The bis-azide is preferably present in the top layer 206 in an amount offrom about 2% to about 40% by weight, more preferably from about 4% toabout 25% by weight, and most preferably from about 5% to about 10% byweight.

Water-soluble polymers that undergo crosslinking by bis-azides aresuitable materials for preparing the top layer 206. Examples include,but are not limited to, polyvinyl pyrrolidone, copolymers of vinylpyrrolidone, acrylamide-diacetone acrylamide copolymer, polyacrylamide,copolymers of acrylamide, gelatin, and mixtures thereof.

Water-soluble polymers that may or may not be crosslinked by bis-azidesin amounts up to about 40% of the weight of the top layer 206 can alsobe incorporated. Such materials are used to improve coating quality andadhesion. They include polyvinyl alcohol, cellulose,carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose,hydroxypropylcellulose, polystyrene sulfonic acid, polyacrylic ormethacrylic acid, and mixtures thereof. Aromatic diazonium salts may beadded at low concentrations to the top layer 206 to improve adhesion.Inorganic pigments such as silica, alumina, clays, and titanium dioxidemay be added to improve the hydrophilic properties of the top layer 206.

Another class of compounds that can insolubilize water-soluble polymersby photo-crosslinking are aromatic diazonium salt-containing compounds.They are prepared by the condensation of aromatic diazonium saltcompounds and a condensation agent. Formaldehyde is a preferredcondensation agent. Other condensation agents that can be used accordingto the invention include various bis-(alkoxymethyl) diphenyl ethers.Preferred diazonium salt-containing compounds are 4-diazodiphenylaminesulfate, 3-methoxy-4-diazodiphenylamine sulfate, 4-phenoxydiazobenzenezinc chloride double salt, and 2,5-dimethoxy-4-tolylmercaptodiazobenzenezinc chloride double salt. Preferred counter-anions of the aromaticdiazonium salts include zinc chloride, sulfate, and mixtures thereof,chloride, dihydrogen phosphate, mixtures of zinc chloride, sulfate andphosphate, and methyl sulfonate. Other counter-ions can also be used.

The diazonium salt-containing compound is preferably present in the toplayer 206 in an amount of from about 5% to about 50% by weight, morepreferably from about 10% to about 40% by weight, and most preferablyfrom about 15 to about 20% by weight.

The diazonium salt-containing compounds can undergo self-crosslinking tocause insolubilization of the top layer 206 without any participation ofthe constitutive polymer. A host of water-soluble polymers may thereforebe used in the top layer 206 according to the invention. They include,but are not limited to, polyvinyl alcohol, carboxymethylcellulose,hydroxymethylcellulose, hydroxyethylcellulose,hydropropylpropylcellulose, polyacrylic or methacrylic acid, polyvinylpyrrolidone, copolymers of vinyl pyrrolidone, polyacrylamide, copolymersof polyacrylamide, gelatin, and mixtures thereof.

Suitable oleophilic materials for top layer 206 include acrylate,methacrylate, and vinyl compounds of polyesters, polyurethanes,polyepoxides, bisphenol A resins, and phenoxy resins among others.

Alternatively, the top layer 206 can comprise a mixture of water-solublemonomers and initiators of photo-polymerization. Examples ofwater-soluble monomers suitable for preparing the top layer 206according to the invention include, but are not limited to, acrylamide,diacetone acrylamide, N,N′-methylenebisacrylamide, N,N′-ethylenebisacrylamide, diacrylamide, omega acrylamidocaproic acid, piperazinediacrylamide, acrylyl pyrollidone, and mixtures thereof.

Water-soluble photoinitiators that can be used with these water-solublemonomers include, but are not limited to, ceric ammonium oxalate,manganic ammonium oxalate, and photoreducible dyes such as methyleneblue, eosin yellow, erythrosin, and rose bengal. These photoreducibledyes require a co-catalyst. A tertiary amine, such as trimethylamine,triethanolamine, and others, can be used. A preferredphoto-polymerization initiator is2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthene-2-yloxy)-N,N,N-trimethyl-1-propanaminiumchloride together with triethanolamine as a co-catalyst.

As a further alternative, the top layer 206 may be prepared by polyvinylalcohol containing photo-crosslinking groups. The synthesis andcharacteristics of highly photosensitive polymers derived from polyvinylalcohols that contain stilbazolium groups at low mole percent, even lessthan 1 mole percent, is well known and described, for example, in J. ofPoly. Sci.: Poly. Letters Ed., 18:613 (1980). Such materials arecommercially available from Toyo Gosei (Ichikawa City, Japan) and EsprixTechnologies (Sarasota, Fla.). They are sold as viscous aqueoussolutions which upon dilution with water can be coated. They are stableand are effectively crosslinked by light exposure. Their peak lightabsorption ranges from 342 to 380 nm. Additives such as aromaticdiazonium salt-containing compounds can be added to improve adhesion.

The optional use of a thin layer of an aromatic diazoniumsalt-containing compound between an oleophilic intermediate layer 204and hydrophilic top layer 206 of the positive plate 200 has been foundto significantly improve adhesion. For this purpose, the previouslydescribed diazonium salt-containing compounds are preferred. Diazoresins that are solvent-soluble may also be used. Their counter-anionsinclude, but are not limited to, toluene sulfonate, tetrafluoroborate,and hexafluorophosphate. The diazonium salt-containing compounds arecoated onto the oleophilic layer 204 from dilute solutions and may havesurfactant additives.

A desirable feature of a photosensitive plate that is imaged by inkjetprinting is that the plate should be unaffected by exposure to ambientlight. The plate can then be imaged without any shielding from roomlight. This feature can be achieved in the positive plate 200 of thisinvention by incorporating colorants into the photosensitive top layer206 that absorb at wavelengths of photosensitivity of the photosensitivetop layer 206. The dye concentration should be high enough to enable thecoating to be unaffected by exposure to room light and low enough toenable the photoreaction to occur when the top layer 206 isblanket-exposed to more intense radiation. Suitable dyes and pigmentsfor this purpose include, but are not limited to, Acid Yellow 25 (C.I.18835), Acid Yellow 29 (C.I. 18900), Acridine Yellow G (C.I 0.46025),Basic Yellow 2 (C.I. 41000), and aqueous dispersions of carbon black andyellow pigments.

Suitable imaging fluids 208 for imaging the printing member 200 includechemicals that inhibit photoreaction. Antioxidants, for example, can beused to inhibit the photoreaction. Suitable antioxidants for use inimaging fluids 208 according to the invention include, but are notlimited to, hydroquinone, 4-methoxyphenol,2,6-di-(t-butyl)-4-methylphenol,2,2′-methylenebis-(4-methyl-6-t-butylphenol), diesters ofthiodipropionic acid, triarylphosphite, and the nitroso dimer inhibitingsystem described in British Patent No. 1,453,681.

Alternatively, masking agents can be used as the imaging fluid 208.Examples are dyes or pigments that absorb at wavelengths ofphotosensitivity of the photosensitive top layer 206. They include, butare not limited to, Acid Yellow 25 (C.I. 18835), Acid Yellow 29 (C.I.18900), Acridine Yellow G (C.I 0.46025), Basic Yellow 2 (C.I. 41000),and aqueous dispersions of carbon black and yellow pigments. Imagingfluids 208 may also be prepared by combining the two types of activeagents listed above.

Although imaging methods involving imagewise applying a masking agent ona positive-working printing plate have been disclosed (see, e.g., U.S.Pat. No. 6,245,486), current positive-working plates typically have anoleophilic top layer which becomes soluble when exposed to ultravioletradiation. A masking agent is applied imagewise on the top layer toprevent solubilization of the imaged area. Similar to negative-workingprinting plates, currently available positive-working printing platesrequire removal of the non-image areas to reveal the hydrophilic layerunderneath to create an imagewise lithographic pattern.

In contrast, the construction of printing member 200 allows an imagingmethod that requires only the imaged area to be removed. Since the imageof typical imaged lithographic plates represents about 20 to 30% of theplate surface area, only a small portion of the top layer 206 needs tobe removed. Accordingly, less coating is accumulated in the developer,and the developer can last longer in the present invention. The printingmember 200, therefore, offers benefits that were not previouslyavailable.

It will be seen that the foregoing techniques provide a basis forimproved lithographic printing and superior plate constructions. Theterms and expressions employed herein are used as terms of descriptionand not of limitation, and there is no intention in the use of suchterms and expressions of excluding any equivalents of the features shownand described or portions thereof. Instead, it is recognized thatvarious modifications are possible within the scope of the inventionclaimed.

1-15. (canceled)
 16. A method of imaging a lithographic printing member,the method comprising the steps of: (a) providing a printing membercomprising a photosensitive top layer having a first lithographicaffinity and a layer thereunder having a second lithographic affinityopposite to the first lithographic affinity, the top layer comprising amaterial which, upon subjection to an imaging fluid, becomescrosslinkable by exposure to actinic radiation; (b) dispensing theimaging fluid in an imagewise pattern; (c) exposing the printing memberto actinic radiation, thereby crosslinking portions of the top layerthat have received imaging fluid; (d) subjecting the printing member toa solvent, the solvent disrupting non-image, uncrosslinked portions ofthe top layer; and (e) removing the non-image portions of the top layer,thereby creating an imagewise lithographic pattern on the printingmember.
 17. The method of claim 16 wherein the solvent comprises anaqueous fluid.
 18. The method of claim 16, wherein the firstlithographic affinity is hydrophilicity and the second lithographicaffinity is oleophilicity.
 19. The method of claim 16, wherein the firstlithographic affinity is oleophilicity and the second lithographicaffinity is hydrophilicity.
 20. The method of claim 16, wherein the toplayer comprises at least one crosslinkable moiety.
 21. The method ofclaim 20, wherein the crosslinkable moiety is selected from the groupconsisting of multifunctional acrylic monomer, multifunctional acrylicoligomer, multifunctional acrylic macromer, and combinations thereof.22. The method of claim 16, wherein the imaging fluid comprises amultifunctional amine.
 23. The method of claim 16, wherein the top layercomprises at least one photo-polymerizable moiety and a first componentof a two-component photo-polymerization initiating system.
 24. Themethod of claim 23, wherein the imaging fluid comprises a secondcomponent of a two-component photo-polymerization initiating system.25-95. (canceled)